Couplings of this type are above all used for filling tank lorries and the like from the bottom, the male portion as well as the female portion then having self-closing valve which are opened upon interlocking of the two coupling members, generally by means of a locking device of the bayonet catch type. In previously known couplings during a locking phase rolls are caused due to the relative rotation to run in inclined cam grooves arranged in the inner surface of the female member. The rolls are mounted on a transversal shaft in the female member housing, said shaft being connected to the valve piston in the female member. In this way that valve piston is urged into the male member whereby there is formed a through opening so that liquid or gas can freely flow through the coupling.
Especially in the above-mentioned use where the male member is located at the bottom of the tank, the interconnection of the two coupling members must often take place in narrow spaces calling for a sharp bending of the thick hose which in most cases has a diameter of 6-8 cms and thick walls in order to withstand the rather high pressures--often of the size of magnitude 0.7-1.0 Pa. This results in the coupling often being exposed to very powerful breaking stresses acting upon the connection between the male and the female members.
In known hose couplings these stresses cause problems involving inter alia material friction, especially between the rolls and the shaft on which said rolls are mounted, and between the rolls and the cam grooves. This problem is amplified by the fact that, in prior art embodiments, it was necessary to use a short actuator acting upon the piston resulting in an unsatisfactory stability in the coupling. For that reason certain couplings comprise a spring package making the structure stiffer.
A further example of the standing of the art is described in U.S. Pat. No. 3,441,055 (Pickell).